1. Field of the Invention
The invention relates to an integrated circuit charge pump, and more particularly to a charge pump with a single HVPMOS transistor as a main switch having coupled in parallel to its source and extended drain a bulk switch with fixed bulk connection.
2. Description of the Related Art
Reference is made to A New Charge Pump Without Degradation in Threshold Voltage Due to Body Effect by Jongshin Shin, In-Young Chung, Young June Park, and Hong Shick Min in the IEEE Journal of Solid-State Circuits, Vol. 35, No. 8, August 2000.
U.S. Patent Application 2005/0088220 (Hahn et al.) discloses a charge pump circuit which alleviates the body effect of a charge transfer transistor, thereby improving the charge transfer efficiency of the charge transfer transistor. This circuit, however, uses two transistors in series which has the above mentioned problems of a large on-resistance and charge current losses.
U.S. Pat. No. 7,276,960 (Peschke) presents voltage regulated charge pump with regulated charge current where the amount of current depends on the output voltage error. Voltage overshoots are reduced through pulse skipping. The charge pump circuit comprises a flying capacitor coupled to a CMOS driver on the lower plate and diodes on the upper plate.
U.S. Pat. No. 6,995,995 (Zeng et al.) teaches a DC/DC converter where charge pumps operate in two-phase cycles including a charge phase and a pump phase and where the bulk terminal is tied to the source of the switching transistor. Switches are segmented and segments contain a plurality of identical transistors coupled in parallel.
U.S. Pat. No. 6,977,533 (Kernhof et al.) describes a 32V H-Bridge Driver where a charge pump comprises a non-overlapping two-phase clocking scheme where during the pre-charge phase a first capacitor is charged and where during the following shuffle phase this charge is reloaded into a second capacitor. The switches involved are high-voltage N and P CMOS transistors.
U.S. Pat. No. 6,400,211 (Yokomizo et al.) shows another DC/DC converter where a first set of two switches charge a first capacitor during a first phase, and where a second set of switches charges a second capacitor during a second phase, where the second phase is the inverse of the first phase. The input voltage to the DC/DC converter is about 3.6 Volt, typical of a Lithium Ion battery.
U.S. Pat. No. 6,831,499 (Oddone et al.) teaches a Negative Charge Pump which has a plurality of operating phases and stages, each stage comprising of at least two n-channel MOS transistors with bulk regions and parasitic bipolar transistors. The bulk regions are coupled during the operating phases to a potential such that the parasitic bipolar transistors will not turn on.
It should be noted that none of the above-cited examples of the related art provide the advantages of the below described invention.